Hello Alice,

It can take a while (several months) for a bruise under a nail to grow up, but as you have posted here I expect you are worried about the possibility of this being a type of skin cancer (melanoma) that can occur under a nail. This is quite rare so just for this reason alone it would be unlikely, even so, to be on the safe side it would be a good idea to get someone to take a look and check it out.

No one here on Cancer Chat will be able to say for sure what it is. Our advice in situations like this is to make a GP appointment and get their input. I hope you can arrange this easily and that they can put your mind at rest. 

Best wishes, 

Julia